1. Field of the Invention
The present invention relates to a stencil printing machine having a printing drum in a cylindrical shape in which perforated stencil sheet is made to wrap on an outer circumferential surface thereof and which is driven to rotate.
2. Description of the Related Art
There has been known a stencil printing machine having a printing drum in a cylindrical shape. An explanation will be given of an example of a structure of the stencil printing machine. The printing drum of the stencil printing machine is provided with a porous and cylindrical supporting member and a mesh screen layer which is made to wrap on an outer circumferential surface of the supporting member. At an inner portion of the printing drum, there is provided ink supplying means for supplying ink onto an inner circumferential face of the printing drum. On an outer side of the printing drum, there is provided a press roller as pressing means in proximity to the printing drum. Stencil sheet is made to wrap on an outer circumferential surface of the printing drum. The printing drum and the pressing means are rotated and print sheet is supplied therebetween. Ink supplied to the inner circumferential face of the printing drum, is transcribed onto the print sheet after passing through opening portions of the supporting member, the mesh screen layer and perforations of the stencil sheet to thereby form an image.
According to the above-described machine, prior to printing operation, a reading apparatus reads image of original and converts the image into electric signals. In accordance with the signals, a stencil making apparatus having a heat generating element such as a thermal head or the like perforates the stencil sheet. Further, the perforated stencil sheet is made to wrap on the outer circumferential surface of the printing drum and thereafter, the printing operation is carried out as described above.
According to the above-described machine, generally, when there causes a shift between printed image and draft image, there is carried out image adjustment in the longitudinal direction and the lateral direction.
Correction of image shift in the longitudinal direction is disclosed in Japanese Patent Laid-Open No. 66308/1975. Correction of image shift in the horizontal direction (lateral direction) is disclosed in Japanese Patent Laid-Open No. 218435/1988.
Further, in an offset printing machine, an aluminum plate is used as a printing plate. The aluminum plate is used by fixing a front end portion thereof by a clamp apparatus and making the aluminum plate wrap on a plate cylinder. A used aluminum plate is provided with considerable strength. All of the face of the aluminum plate is not fixed by the plate cylinder. Hence, in order to adjust a shift of the printed image, the aluminum plate is directly moved by a meandering adjusting member by pivoting the clamp apparatus holding a front end portion of the aluminum plate or moving the aluminum plate in a circular arc shape or the like.
However, according to the above-described conventional stencil printing machine, there poses a problem in which although image shift in the longitudinal direction or the lateral direction can be adjusted, image shift in a skewed direction cannot be adjusted. Further, when the structure of the offset printing machine is applied to the stencil printing machine, the strength of the stencil sheet is extremely smaller than that of the aluminum plate and therefore, there causes a problem in which wrinkle is formed in the stencil sheet or the like.
Japanese Patent Laid-Open No. 344648/1994 discloses a technology for carrying out skew adjustment of image by twisting a printing drum on which stencil sheet is made to wrap. However, strength of the printing drum is small since there are formed a number of perforations for passing ink at a portion of a peripheral wall thereof. Therefore, when the printing drum is twisted as described above, unreasonable stress is generated in the printing drum and there causes a problem of destruction or the like.
According to the present invention, the above-described problem is alleviated and image skew adjustment is carried out simply and without generating unreasonable stress in the printing drum.
According to a first aspect of the present invention, there is provided a stencil printing machine comprising a base member (15) having rigidity and rotated around a central axis line of its own, an ink-permeable member (2) mounted to the base member along a rotational direction and forming a circumferential surface for attaching stencil sheet, and skew adjusting means (30, 40) for moving the ink-permeable member relative to the base member in a skewed direction which is not in parallel with both of the central axis line and the rotational direction.
According to a second aspect of the present invention, there is provided a stencil printing machine according to the first aspect, wherein the skew adjusting means (30, 40) moves a side of one end portion of the ink-permeable member (2) in the skewed direction.
According to a third aspect of the present invention, there is provided a stencil printing machine according to the second aspect, wherein the ink-permeable member is pivotable relative to the base member (15) centering on a substantially central portion in the central axis line direction at one end side of the ink-permeable member (2).
According to a fourth aspect of the present invention, there is provided a stencil printing machine according to the third aspect, wherein a side of the other end portion of the ink-permeable member (2) is made movable relative to the central axis line.
According to a fifth aspect of the present invention according to the first aspect, there is provided a stencil printing machine, wherein the skew adjusting means (30, 40) moves the side of the one end portion and a side of the other end portion of the ink-permeable member (2) in the skewed direction in cooperation with each other.
According to a sixth aspect of the present invention, there is provided a stencil printing machine comprising, a pair of circular plate members (16) arranged coaxially on a common central axis line and a base member (15) having a first base member (connecting base plate 17) for connecting the pair of circular plate members and rotated around the central axis line. Next, the stencil printing machine is further provided with a second base member (clamping base plate 18) attached pivotally to the first member, clamping means (3) provided to the second base member, and an ink-permeable member (2). The ink-permeable member is provided with one end portion attached to one end portion of the second base member, a pair of side edge portions which are made to wrap on the pair of circular plate members along a rotational direction of the base member and the other end portion attached to the other end portion of the second base member, to thereby form a circumferential surface for attaching stencil sheet, one end portion of which is fixed to the clamping means. Further, the stencil printing machine is provided with skew adjusting means (30) provided to the circular plate member for moving the ink-permeable member in a skewed direction which is not in parallel with both of the central axis line and the rotational direction by pivoting the second base member relative to the first base member.
According to a seventh aspect of the present invention, there is provided a stencil printing machine according to the sixth aspect further comprising an engaging portion (25) formed at the other end portion of the second base member (clamp base plate 18), an elastic member (spring 34) for connecting the other end portion of the ink-permeable member (2) to the engaging portion, wherein when the second base member is moved in the skewed direction by the skew adjusting means (30), a side of the other end portion of the ink-permeable member is moved relative to the central axis line.
According to an eighth aspect of the present invention, there is provided a stencil printing machine comprising a pair of circular plate members (41) arranged coaxially on a common central axis line and a base member (15) having a first base member (connecting base plate 17) for connecting the pair of circular plate members and rotated around the central axis line. Next, the stencil printing machine is provided with a second base member (clamp base plate 18) attached pivotally to the first member, clamping means (3) provided to the second base member, and an ink-permeable member (2). The ink-permeable member is provided with one end portion attached to one end portion of the second base member, a pair of side edge portions which are made to wrap on the pair of circular plate members along a rotational direction of the base member and the other end portion attached to the other end portion of the second base member, to thereby form a circumferential surface for attaching stencil sheet, one end portion of which is fixed to the clamping means. Further, the stencil printing machine is provided with skew adjusting means (40) having a moving member (43) provided to the circular plate member to be pivotable around the central axis line and connected with a side edge portion of the second base member for moving the ink-permeable member in a skewed direction which is not in parallel with both of the central axis line and the rotational direction by pivoting the second base member relative to the first base member by moving the moving member.
According to a ninth aspect of the present invention, there is provided a stencil printing machine according to the eighth aspect, further comprising a first gear portion (51) formed at the other end portion of the second base member (clamping base plate 18), and a second gear portion (52) provided on a side of the other end portion of the ink-permeable member (2) and engaged with the first gear portion (52), wherein when the second base member is moved in the skewed direction by the skew adjusting means (40), the side of the other end portion of the ink-permeable member is moved in the skewed direction.
According to a tenth aspect of the present invention, there is provided a stencil printing machine comprising a base member in a cylindrical shape having a rigid peripheral wall having an ink-permeable opening area and rotated around a central axis line of its own, an ink-permeable member mounted to an outer circumferential surface of a peripheral wall of the base member along a rotational direction of the base member and attached with stencil sheet, and skew adjusting means for moving the ink-permeable member relative to the base member in a skewed direction which is not in parallel with both of the central axis line and the rotational direction.